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23 Multiple choice questions

  1. Variable names are case-sensitive. So, for example,$This_Variable is not the same as $this_variable.
  2. To convert one variable type to another, reference it and PHP will automatically convert it for you.
  3. You can use \' or \" to escape either a single or double quote.
  4. A hyphen is reserved for the subtraction operators. A construct like $current-user would be harder to interpret if hyphens were also allowed in variable names and, in any case, would lead programs to be ambiguous.
  5. They are provided by the PHP environment but are global within the program, accessible absolutely everywhere. All of the superglobals (except for $GLOBALS) are named with a single initial underscore and only capital letters;
  6. Variables hold a value that can be a string, a number, or other data.
  7. Generally, the operators && and and are interchangeable except where precedence is important, in which case && has a high precedence, while and has a low one.
  8. $variable = 1 is an assignment statement, whereas $variable == 1 is a comparison operator. Use $variable = 1 to set the value of $variable. Use $variable == 1 to find out later in the program whether $variable equals 1. If you mistakenly use $variable = 1 where you meant to do a comparison, it will do two things you probably don't want: set $variable to 1 and return a true value all the time, no matter what its previous value was.
  9. Using the htmlentities function for sanitization is an important practice in any circumstance where user or other third-party data is being processed for output, not just with superglobals.
  10. With the exception of constants, all PHP variables must begin with $.
  11. When you combine a string with a number, the result is another string.
  12. The purpose of functions is to separate discrete sections of code into their own, self-contained sections that can be referenced by a single function name.
  13. The tag used to start PHP interpreting code is <?php ... ?>, which can be shortened to <? ... ?> but is not recommended practice.
  14. You cannot use spaces in variable names, as this would confuse the PHP parser. Instead, try using the _ (underscore).
  15. You can use multiple lines within quotations marks or the <<<_END ... _END; construct to create a multiline echo or assignment. The closing tag must begin at the start of a line, and end with a semicolon followed by a new line.
  16. You cannot redefine constants because, by definition, once defined they retain their value until the program terminates.
  17. The echo and print commands are similar in that they are both constructs, except that print behaves like a PHP function and takes a single argument, while echo can take multiple arguments.
  18. There is no difference between ++$j and $j++ unless the value of $j is being tested, assigned to another variable, or passed as a parameter to a function. In such cases, ++$j increments $j before the test or other operation is performed, whereas $j++ performs the operation and then increments $j.
  19. All PHP statements must end with a semicolon (;).
  20. If you generate data within a function, you can convey the data to the rest of the program by returning a value or modifying a global variable.
  21. You can use // for a single-line comment or / ... / to span multiple lines.
  22. Are never reset and are only within the scope of the function. You cannot assign the result of an expression in their definitions.
  23. You can make a variable accessible to all parts of a PHP program by declaring it as global.